A common urban legend is that a few drops of Visine in an unsuspecting victim’s drink will cause a harmless bout of diarrhea. This will not produce diarrhea, but oral administration of Visine can induce dangerous side effects related to Visine’s ingredient tetrahydrozoline hydrochloride such as:
Dangerously low body temperature (hypothermia)
Blurred vision
Nausea and vomiting
Difficulty in breathing or even a complete halt in breathing
Elevating (hypertension) then dropping (hypotension) blood pressure
Possible coma
Seizures and tremors
Pfizer recommends that anyone ingesting Visine get medical attention or contact a poison control center immediately.

ok, you need to tell your parents and you need to dump this friend. For gods sake what if he’d made your sister very ill, she could have died. Why the hell would he do that to her? was this supposed to be a joke? There is a very old saying sweetheart, blood is thicker than water, and you should be protecting your sister from things like this. Your friend needs proper help honey before he turns into the kind of sick freak who thinks its clever to dope girls drinks with rohypnol or worse. Look after your sister please honey, because this world is dangerous enough, and thank god she’s ok.
hugs xx

@klutzaroo just read the link you sent, that is pretty scary stuff, and enough idiots out there thinking what a laugh it is to slip this stuff into folks drinks. Terrifying. Thank you for the link <hugs> xx